First detection of cold dust in the northern shell of NGC5128 (Centaurus A)

M Stickel*, JM van der Hulst, JH van Gorkom, D Schiminovich, CL Carilli

*Corresponding author for this work

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Abstract

Deep far-infrared (FIR) imaging data obtained with ISOPHOT at 90 mum, 150 mum, and 200 mum detected the thermal emission from cold dust in the northern shell region of NGC5128 (Centaurus A), where previously neutral hydrogen and molecular gas has been found. A somewhat extended FIR emission region is present in both the 150 mum and 200 mum map, while only an upper flux limit could be derived from the 90 mum data. The FIR spectral energy distribution can be reconciled with a modified blackbody spectrum with very cold dust color temperatures and emissivity indices in the range 13K <T(Dust) <15.5K and 2 > beta > 1, respectively, where the data favor the low temperature end. A representative value for the associated dust mass is M(Dust) approximate to 7 x 10(4) M(.), which together with the HI gas mass gives a gas-to-dust ratio of approximate to300, close the average values of normal inactive spiral galaxies. This value, in conjunction with the atomic to molecular gas mass ratio typical for a spiral galaxy, indicates that the interstellar medium (ISM) from the inner part of a captured disk galaxy is likely the origin of the outlying gas and dust. These observations are in agreement with recent theoretical considerations that in galaxy interactions leading to stellar shell structures the less dissipative clumpy component of the ISM from the captured galaxy can lead to gaseous shells. Alternatively, the outlying gas and dust could be a rotating ring structure resulting from an interaction or even late infall of tidal material of a merger in the distant past. With all three components ( atomic gas, molecular gas, dust) of the ISM present in the northern shell region, local star formation may account for the chains of young blue stars surrounding the region to the east and north. The dust cloud may also be involved in the disruption of the large scale radio jet before entering the brighter region of the northern radio lobe.

Original languageEnglish
Pages (from-to)95-102
Number of pages8
JournalAstronomy & astrophysics
Volume415
Issue number1
DOIs
Publication statusPublished - Feb-2004

Keywords

  • galaxies : individual : NGC5128
  • galaxies : elliptical & lenticular, cD
  • galaxies : intergalactic medium
  • infrared : general
  • infrared : galaxies
  • FAR-INFRARED EMISSION
  • RECENT STAR-FORMATION
  • NEARBY GALAXIES
  • MOLECULAR GAS
  • NEUTRAL HYDROGEN
  • MERGER REMNANTS
  • RADIO GALAXY
  • BIMA SURVEY
  • NGC 5128
  • HI RING

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